寡头卖主垄断一种由少数卖方控制的市场状况。因为卖主极少，以至卖主的任何行为都可能对价格产生实质影响，从而对其竞争对手产生相当大的冲击影响力

A market condition in which sellers are so few that the actions of any one of them will materially affect price and have a measurable impact on competitors.